When a boy takes the first puff of a cigarette, he's probably thinking about kids — the kids at school, on the playground, and in the neighborhood who are smoking, too. He's probably not thinking of the kids he might father someday. The findings of a lengthy study suggest that a boy's use of cigarettes today may have a dramatic effect on the kids he'll have someday, especially his sons. Boys who start smoking before puberty are more likely to have overweight sons.
Eleven seems to the the turning point where smoking boys have overweight sons. The study found that boys who start smoking before age 11 have sons who are, on average, 11 to 22 pounds heavier than their 13- to 17-year-old peers. Ironically, the fathers themselves tend to be skinny.
The study began in the 1990s at the University of Bristol in the United Kingdom. The Avon Longitudinal Study of Parents and Children began with 14,541 pregnant women in the county of Avon, England. Due dates for the women ranged from April 1, 1991, through December 31, 1992. The women's partners were invited to join the study but their participation wasn't mandatory.
The partners who did choose to join were given questionnaires about their lifestyles, including their smoking habits. Of the 9,886 fathers who joined the study, 5,451 identified themselves as smokers, either currently or at some point in their past. Other smoking-related questions included at what age they began smoking regularly and if they were smoking at the time of their child's conception.
Most of the smoking fathers reported beginning at age 16 but 3% of them (166 individuals) said they were smoking regularly at age 11, before signs of puberty emerged.
Years later, when the children born during the study were between ages 7 and 17, they underwent evaluations that included body mass index (BMI), waist circumference, and total-body fat-mass scans. The girls reported when they first started menstruating and boys were asked about male indicators of puberty that included pubic hair growth.
The study revealed:
- Smoking did not influence whether a man fathers girls or boys.
- Maternal smoking, beginning at any age, had no effect on her children's BMI.
- The girls' BMIs were not much different between ages 7 and 11, but after age 11, the BMI of the girls born to fathers who started smoking before age 11 began to rise higher each year than their peers born to fathers who started smoking later or never smoked. BMI differences never reached the point of being statistically significant.
- From ages 7 to 17, the BMI of the boys fathered by boys who smoked before age 11 was higher than all the other boys; the difference in BMI grew larger each year, especially at and beyond puberty, until age 17 when they were no longer being studied.
- Between ages 13 and 17, the sons of early smokers carried 11 pounds to 22 pounds more body fat than their peers.
- The waist sizes of the sons of smokers were about two inches bigger, on average.
- 46% of the boys born to early smokers were smoking regularly themselves by age 17.
- The smoking habit of the sons had no effect on their own BMI, body fat, or waist circumference.
Source: Pembrey, Marcus, et al. "Prepubertal start of father's smoking and increased body fat in his sons: further characterisation of paternal transgenerational responses." European Journal of Human Genetics. Nature Publishing Group. Apr 2, 2014. Web. Apr 14, 2014.